Compositions of liquid paraffins containing mixtures of alkyl-substituted polynuclear aromatic hydrocarbons as swelling agents



United States Patent COMPOSITIONS OF LIQUID PARAFFINS CON- TAINING MIXTURES OF ALKYL-SUBSTITUTED POLYNUCLEAR AROMATIC HYDROCARBONS AS SWELLING AGENTS Clayton W. Nichols, Jr., Huntington, and Melvin I. Smith, Rockville Centre, N.Y., assignors to Mobil Oil Corporation, a corporation of New York No Drawing. Continuation-impart of application Ser. No. 385,799, July 28, 1964. This application Oct. 16, 1968, Ser. No. 768,174

Int. Cl. C09k 3/00, 3/02; C10m 1/16 US. Cl. 252-72 2 Claims ABSTRACT OF THE DISCLOSURE Compositions comprising liquid paraffins containing a small amount, sufficient to act as a swelling agent, of a mixture of alkyl-substituted polynuclear aromatic hydrocarbons comprising alkyl naphthalenes, acenaphthylenes, phenanthrenes and pyrenes.

CROSS REFERENCE TO RELATED APPLICATIONS Continuation-in-part of application Ser. No. 385,799, filed July 28, 1964, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention, which is a continuation-in-part of our copending application Ser. No. 385,799, filed July 28, 1964, relates to liquid hydrocarbon compositions, particularly suitable for use as hydraulic or lubricating oils, having improved rubber-swell characteristics. More particularly, in this aspect, the invention relates to hydraulic or lubricating oils having the aforementioned improved rubber-swell characteristics, in which these desirable properties of the oil are retained during its use.

Description of the prior art Prior to the present invention, oils employed for hydraulic or lubricating purposes, under conditions in which the oil is being retained within a sealed area, have been comprised of predominantly naphthenic hydrocarbons, in preference to paraffiuic hydrocarbons, inasmuch as it was found that the use of paraflinic oils, in many systems, resulted in loss of lubricant which occurred largely past seals and packings. The use of naphthenic oils, on the other hand, was found to result in minimizing such leakage; whereas the use of paraifinic oils, apart from the leakage problem, is highly attractive, inasmuch as the paraifinic oils are more stable to deterioration by oxidation, afford better wear protection, and, in many instances, possess better viscosity indexes. It has been found, however, that the paraflinic oils do not possess the ability to swell seals and packings, to result in a tighter closure and thus minimize leakage in the system. Hence, the ability to employ paraflinic hydrocarbon oils in hydraulic or lubricating "ice systems, which will not result in leakage past seals or packings, is highly desirable from a practical standpoint.

SUMMARY OF THE INVENTION In accordance with the present invention, it has now been found that improved liquid paraflinic hydrocarbons, suitable for use as hydraulic or lubricating oils and possessing the aforementioned advantages of oxidation stability, improved wear protection and high viscosity indexes, can be provided without the aforementioned dis-. advantages of leakage past seals and packing, by incorporating in such oils small quantities of a mixture of alkyl-substituted polynuclear aromatic hydrocarbons, as swelling agents, as more fully hereinafter described. In this respect, it has been found that the use of even small quantities of the aforementioned aromatic hydrocarbons causes rubber or packings in enclosed systems to swell, thereby making for a tighter closure and minimizing, or completely avoiding leakage. In this manner, all of the advantages of parafiinic hydrocarbons over naphthenic hydrocarbons are realized, without encountering the aforementioned leakage problems.

More specifically, in accordance with the present invention, the lubricating oil vehicle may comprise any liquid paraffinic hydrocarbon, or liquid hydrocarbons which are predominantly paraffinic in character. Thus, for example, the lubricating oil may comprise, in a preferred form, a liquid paraffinic petroleum hydrocarbon, or liquid petroleum hydrocarbons which are predominantly paraffinic in character. This paraffinic lubricating oil may, therefore, comprise any of the conventional paraffinic hydrocarbon oils of lubricating viscosity, and may include mineral or synthetic lubricating oils. The mineral lubricating oils, which are preferred as the lubricating vehicle, may be of any suitable lubricating viscosity, ranging from about 45 SUS at 100 F. to about 2000 SUS at 100 F. These oils may have viscosity indexes varying from about to about 100 or higher. Viscosity indexes from about to about are preferred. The average molecular weights of these oils preferably range from about 250 to about 800.

The alkyl-substituted polynuclear aromatic hydrocarbons employed in combination with the aforementioned parafiinic hydrocarbons, as swelling agents, are present in the form of a mixture of alkyl-substituted polynuclear aromatic hydrocarbons comprising, by Weight, from about 15 to about 25 percent alkyl naphthalenes, from about 15 to about 30 percent acenaphthylenes, from about 35 to about 55 percent phenanthrenes and from about 1 to about 5 percent pyrenes. In general, such mixtures have a boiling point of at least about 400 F. and usually a boiling point from about 400 F. to about 1000 F. Most preferred are mixtures of the aforementioned components which have boiling points from about 480 F. to about 1000 F. A more detailed description of these alkyl-substituted polynuclear aromatic hydrocarbons is disclosed in US. Patent 3,062,771, issued Nov. 6, 1962, and such disclosure is incorporated herein by reference. In general, although it is desirable to employ a pure alkyl-substituted polynuclear aromatic hydrocarbon oil in combination with the aforementioned paraflinic oil vehicle, it is extremely difiicult, from a commercial standpoint, to produce a substantially pure product. However, the use of thermal or catalytic processes results in the build-up of the aromatic fractions and a cracking of the parafiinic fractions, which, therefore, makes it possible to produce a highly aromatic material which can be used either in its entirety in the aforementioned boiling point range, or in any desired intermediate cuts. Analysis for the paraffinic content of the commercially produced aromatic oils by adsorption on silica gel shows that they contain no more than about 8 percent paraflins by volume. The aromatics content, on the other hand, is at least about 90 percent, by volume.

Insofar as the quantity of the alkyl-substituted polynuclear aromatic hydrocarbons, which is employed in combination with the base liquid paraffinic hydrocarbon, is concerned, even small quantities of the aromatic hydrocarbons are effective; however,- compositions are preferred which comprise liquid paraifinic hydrocarbons containing from about percent to about 20 percent, by volume, of the alkyl-substituted polynuclear aromatic hydrocarbons. It should also be noted that the liquid parafiinic hydrocarbon compositions of the present in-.

vention may contain, in addition to the aforementioned alkyl-substituted polynuclear aromatic hydrocarbons, minor amounts of other additive materials such as antiwear, anti-oxidation, or anti-corrosion agents, if so desired.

The chemical and physical properties of a typical mixture of alkyl-substituted polynuclear aromatic hydrocarbons, which may be employed in the novel compositions of the present invention are illustrated by the following Table I:

TABLE I Wt. percent Paraflins 2.2 l-ring naphthenes 0.5 Z-ring naphthenes 0.3 3-ring naphthenes 0.3 4-ring naphthenes 0.3 S-ring naphthenes 0.2 Alkyl benzenes 6.0 Alkyl naphthalenes 20.9 Acenaphthylenes, including acenaphthenes 23.2

DESCRIPTION OF SPECIFIC EMBODIMENTS The following examples will serve to illustrate the efficacy of the novel and improved compositions of the present'invention, containing the aforementioned alkylsubstituted polynuclear aromatic hydrocarbons in minor proportions. In these examples, as more fully hereinafter discussed, the alkyl-substituted polynuclear aromatic hydrocarbons are designated as aromatic oil additive for simplicity. The properties of the aromatic oil additive employed in these examples are indicated in Table I.

In Examples 1 through 5 of the following Table II, are shown the improved rubber swell properties obtained by the addition of the aforementioned aromatic oil additive of Table I, to a 200 SUS paraffinic hydrocarbon oil with respect to a nitrile rubber, tested in accordance with a standard test ASTM D57l-59T using a temperature of 250 F. and an immersion period of 70 hours.

From the data in Table II, it will be noted that the aromatic oil additives of the present invention are markedly effective in achieving the desired degree of rubber swell when used in combination with liquid paraffinic hydrocarbons.

In another series of preferred formulations, three types of the improved liquid parafiinic hydrocarbons of the present invention, containing the aforementioned aromatic oil additive, described in Table I (supra), were tested for their efiicacy as hydraulic oils on a comparative basis with conventional commercially available parafiinic oils, in which the aforementioned aromatic oil additive was not present. The compositions of the aforementioned hydraulic oils which were subjected to comparative tests, are shown in Examples 6, 7, and 8 of the following Table III, in which the various components are expressed in percent by volume.

TAB LE III SUS solvent paratiim. 200 SUS solvent paraflin. SUS solvent bright; Aromatic oil additive of Table I- 1 A zinc dialkyldithiophosphate. 2 An amine derivative of an alkenyl substituted succinic acid.

The characteristics and specifications of the hydraulic oil formulations of Examples 6, 7, and 8, are shown in the following Table IV.

TABLE IV Ex. 6 Ex. 7 Ex. 8

Gravity, API 26. 8 26. 6 25. 9 Pour, F. (max.)- 20 25 Flash, F. (min.) 360 3 360 V scos ty at 100 F. SUS. /155 /210 290/310 V1scos1ty at; 210 F. SUS 43 45 52 Viscosity Index 92 97 100 Color (max.) 2 3 5 Aniline Point, F 200 210 Rust Test (ASTM D66560) Pass Pass Pass Neutralization N o 1. 2 1. 1. 2

In the following Table V, are shown the performance properties of the improved liquid paraflinic hydrocarbon oils containing the aforementioned alkyl-substituted polynuclear aromatic hydrocarbons, as swelling agents, and as represented by the formulation of Examples 6, 7, and 8 of Table III, compared with conventional commercially available oils, in which the aforementioned aromatic oil 5 additives were not present, and in which there was a large proportion of naphthenic hydrocarbons.

F. containing at least about 5 percent by volume of a swelling agent, boiling from about 525 F. to about 700 TABLE V 150 SUS 200 SUS conventional conventional Oil of Oil of Oil of oil oil Ex. 6 Ex. 7 Ex. 8

Viscosity Index 63 71 92 97 100 Rifitglgelg )swell percent vol. increase (D471; 70 hrs.;

Rutter A 9. 7 9.6 8.1 8.6 8.3 Rubber B-.. 16. 5 16. 8 15.2 16. 3 16. 4 Rubber 2. 2.0 1. 7 2. 5 2. 5 13-10 Oxidation Test 1 (40 hrs.; 260 F.):

Percent kinematic viscosity increase at 100 F,.. 54. 7 49. 1 14. 2 11.7 12.6 Neutralization number increase 4. 3 3. 9 0.2 0. 8 1.1 Deposits 0 0 O Hydraulic service test 2 (150 hrs.- 1 000p.

Ring wt. loss, mg 164. 4 2. 4 Vane wt. loss, mg 64. 2 0.9

Total wt. loss, mg

Emulsion test at 130 F 1 Described in ASTM Standards on Petroleum Products and Lubricants, 1956 Edition, pp. 940-943. 2 Wear of a Vickers V-104E pump is measured after running at the stated conditions pumping 3 gallons of oil around a closed circuit consisting of a reservoir, cooler, filter, pump, relief valve, fiowmeter, and

instruments.

3 Moderate-heavy. 4 Less than 3 cc. emulsion after minutes.

From the foregoing pertinent data, the marked superiority of the improved liquid paraifinic hydrocarbons of the present invention containing alkyl-substituted polynuclear aromatic hydrocarbons, as swelling agents, will become apparent when compared with conventional commercially available oils containing a large proportion of naphthenic hydrocarbons in which the aforementioned aromatic oil additives are not present. More specifically, the improved liquid paraffinic hydrocarbons are markedly superior with respect to viscosity index, oxidation stability and wear protection, yet their rubber-swell properties are about the same as the aforementioned conventional oils.

Although the present invention has been described with preferred embodiments, it will be understood that various modifications and adaptations thereof may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily appreciate.

We claim:

1. A liquid paratfinic hydrocarbon composition having a viscosity from about 45 SUS to about 2000 SUS at 100 References Cited UNITED STATES PATENTS 2,816,867 3/1955 Moore et al.

LEON D. ROSDOL, Primary Examiner DAVE SILVERSTEIN, Assistant Examiner US. Cl. X.R. 

